High-pressure modulator tube



Dec. 21, 1948. E. G. F. ARNOTT ETAL HIGH-PRESSURE MODULATOR TUBE Filed June 19, 194s.

INVENTORS B551 @nn/LEY ATTORNEY Patented Dec. 21, 1948 HIGH-PRESSURE MODULAS'IOR .TUBE

Edward G. Arnett, Upper 'Montclair,-Charles M. Slack, Glen Ridge, andGlarence E. Dawley, Bloomfield, N. J., iassignnrs rio `:W.estnglriouse -.Electric Corporation, East BittsbnrghpfPa., a corporation of Pennsylvania Application June`19,

`thetransmission off high frequency waves.

Devices of this general type are'knownto .the art but have heretofore :been subject Yto the disadvantages that they have been .of relatively yshort lifeand operate .at comparatively low voltages. Moreover, they have been erratic or unstable in performance.

`It is laccordingly an object of the .present invention to .provideia triggered spark-'gap-device which `operates under substantiallyvstable conditions during :its useful life.

Another object of the present invention is the provision of a triggered sparkfgap device which requires a relatively low .triggering voltage to initiate a discharge.

Another object of the vpresent invention is the provision of a triggered spark-gap device which operates with low venergy dissipation and uwill pass comparatively high power `after initiation of the main discharge :at much lower .voltages than otherwise.

A further object of the present .invention -is the. provision of a triggered :spark-gap device which lis of simple yet rugged construction sand thus economical to manufacture.

4Still further objects ofA .the `Present `.invention will `loecomexobvious vto those 4skilled `in the-fart by reference to the .accompanying drawing wherein:`

Fig. 1 is an elevational view of .a `:triggered spark-,gap device constructed-in accordance with the present invention; Fig. 2 shows 4a slight modification which .the triggered spark-gap of the presentinventionv may take;

Fig. 3 is an elevational view-showingastillfurther construction which the sparkfgap of the present invention -may have;

. Fig. 4 is a fragmentary .view of another modication of the triggered spark-gapof'the present invention;

Fig. 5 .is a perspective view of,sti11 another modification which the triggered vspark-.gap device of the present invention may ,.take;

Fig. 6 is a View similar to that @of Fig. J5 ,ibut showing a slightly diierent constructionof ,the electrodes of the device, and

. Fig. 7 is a lfragmentary Viewidentcal to .that of .Fig..6 except that one ofthe electrodesfofthe device is insulated for theigreateriportionof .its length.

.Referring Anow to the A.drawings :,in idetail, the

triggered spark-gap `device 5 of fthe present v`in- -vention asvshown iniFigl comprises=an.envelope fliformed of -vitreous isections 1 joined together fby fa metalliceection 18. This 'latter section is f5 likewise formed ofltwoihalvesrwhieh, after com plete fabrication of the ends 'of the device 5, fare-welded Tor otherwise hermetica'lly united `at their ffrespect'ive Vflanges '9. Inorder to form a 'seal with the .vitreous y'envelope vportions l, the .10h-elves of the lmetallic ls'ection y"8 -ia're -made of -a l:metal such as Kovar which-has a coeiiicient :ofwexpansion approximating 'that ofthe vitreous portions "Therespective ends fof the vitreous portions 1 l5 are h'ermetically Iclosed by end caps I0 'likewise -fformedfof "1.Kovar through .whichare sealed a 'pair' of :electrodes @i2 `and i3 formedo'f suitable ametal such asironfortungsten. .As\will`vbe noted, theaopposingelectrodesl2fand |'3 extend into-the `20 '.device to j-approximately lthecenter of the sur.-

rounding metallic cylinder f8 .with 'just a small ispacingzof approximately :.030 vinch between the respective electrode ends.

After fabricatione'ofthe Ydevieeii, it is treated 1325 and `exhausted in `the :customary manner and ithen I:llled :with :an ionizable .medium at fhigh :pressure prior toxsealingfo'fl .at i4. As 4will Vbe hereinafter rfspeciiically zmentioned, the vnature and ipres's'urefof the ionizablefmedium is of conflo .siderable importa-nce :in determining `the operatfing lvoltage :of 'the cidevice :as :its .useful life.

The istructu-re asshown .in Fig .2 differs only .infminor ',cons'tructional :details from .that KVV'of the .well as lbearing on preceding modification. vAs `can'be readily seen,

` the metallic cylindrical center section.f22-.of Fig. 2 is :all ofrone .pieceiandythe electrodes .p23 and 24 fare'sealed to the vitreous `end sections 25 of the venvelope through 1reentrant ^presses 26 :and 21, .thusfdispensing with ,the Kovar end caps l0 of zFig. 1.

The advantage of utilizing ycylinders :as shown in Figs. 1 .and A2 l;is gthatiit allows dimensions to xbe :chosen toygive v a minimum potential gradient ,at ithe: inner cylinder A`and auniform voltage disitributionf'along ,the electrodes. 'I'hisaccordingly .fresultsinwearjor erosion ofithe electrodes being distributed-'over thezentire surface, thus minimizingchangein electrode spacing. PMoreoveigfsince o the metallic cylindrical center :section :surrounds 4the electrodes tfor,y a 1 large Iportion,I of their length :'and'particularly at vthe gap therebetween, the :amount of Icoating-oi theiglasswalls 4byisputtered :metalfisireducedfbecause the-marc At-alses'fplace inside .rthe .zcylinder. .Qtherw-ise `sputtering eventu ally destroys the insulating properties of the vitreous envelope and thus shortens the useful life of the device.

The device of Figs. 1 and 2 operates in the following manner. A potential is applied to the metallic cylindrical center section 8 or 22 and one of the electrodes (I3 or 24, for example) is grounded. When an extremely rapid voltage impulse is applied to the other electrode (I2 or 23) as a trigger electrode, a. discharge is started between the metallic cylindrical electrode 8 or 22 and the remaining grounded electrode I3 or v24. Such discharge is in the form of a lOw voltage arc which passes very high currents due to production of positive ions in the ionizable medium. Since the ionizable medium is at high pressure, large currents of the order of hundreds of am- The modification of Fig. 6 is somewhat similar to that of Fig. 5 in that the main electrodes 62 and 63 are again Kovar Acups sealed to reentrant stems 04. In this instance, however, the-leadin for the electrode 63 enters through a side-arm reentrant-press 65 and the `trigger electrode 66 1- isin theform ofxa rod o'rl pin extending through an opening 6l in the electrode 63 and sealed through a vitreous wall 68 of the envelope 69.

In triggered spark-gap devices of the present invention the operating voltage, as before mentioned, is determined by the spacing between the peres can be maintained without overheating the between of about .030 inch. The smaller dimensioned device operated at from 6 to 12 kilovolts at 1000 cycles when filled with 45 lbs. absolute pressure of nitrogen admixed with lbs.v of air, thus making the total pressure of the ionizable medium slightly over approximately 4 atmospheres. With an admixture of 238 lbs. of argon and 15 lbs. of air (or total of approximately 3.6 atmospheres), the device operates at 4 kv. and with air alone at 15 lbs. (approximately 1 atmosphere) the voltage was 6y kv. while the structure of Fig. 2 operated as high as 18 kv. when constructed of dimensions approaching the upper limits.

In the modification shown in Fig. 3 the 'envelope 32 is `entirely of vitreous vmaterial with the electrodes 33 and 34 sealed through opposite ends of the envelope in the absence of a reentrant press as in Fig. 2. Also, the trigger electrode 35 is sealed into a side-arm 36 and is ring-shaped so as to surround one of the main electrodes 34. Again, as in the previous modifications, the device is filled with an ionizable medium and a voltage impulse is applied between the trigger electrode 35 and the electrode 34 which initiates a discharge between the electrodes 33 and 34 carrying the main voltage. v

The structure of Fig. 4 differs from that of Fig. 3 in that the main electrodes 42 and 43 fare brought into the envelope 44 through side-arm reentrant presses 45, as is the trigger electrode 46, the latter of which is of rod-like configuration similar to the main electrodes 42 and 43;

Fig. 5 shows a construction in which the main electrodes 52 and 53 are in the form of Kovar cups sealed to the reentrant stems 54 and the trigger electrode 55, although sealed to a sidearm reentrant stem 56, is of disc-shape. This provides a uniform field over the surface of the trigger electrode 55 and prevents the triggering spark from producing ions or radiation in the upper gap between the trigger electrode 55 and the main electrode 52. It does, however, initiate the arc between the main electrodes 52 and 53 in the same manner as described in the preceding modications by ionizing the gaseous medium;-

III

comprising an envelope provided with oppositely lkilovolts at a frequency of'500 ythe arc is initiated between electrodes, the gas pressure and the nature of thegas. Likewise the triggering voltage required to initiate the arc between the main electrodes is vdeterminedby the gas pressure and spacing betweenthe trigger electrode and the nearest adjacent main electrode. in Fig. 6 possesses the features of rigidity and ability to withstand high internal pressures and allows for considerable wear of the electrodes dur ing operation before expiration of useful life. In

:addition to the aforementioned gaseous medium,

other gases have been employed such as argon, helium, anda mixture of these latter two gases. Tests with a structure such as shown in Fig. 6

'indicates that a mixture of argon and helium is preferable to either gas alone. This is because the kilovoltage range over which the device operates steadily is much greater with such admixture than with either of the gas-es when used separately, As a specific example of one of such tests wherein the trigger electrode 66 was formed of mil tungsten rod spaced 80 mil from the surrounding adjacent main electrode 63,' and using a 50-50 mixture of argon and helium at a pressure of 75 lbs. absolute (about 5.1 atmospheres), the operating voltage ranged from 8.5 to 13.5 kilovolts. At such rangek the 4triggering voltage required to initiate the arc between the main electrodes B2 and 63`was 6 cycles. This triggering voltage is, however, materially reduced by as much as 50% by the provision of an insulating sleeve yi2 which may be of the same vitreous material as ythe envelope 'I3 as shown in Fig. 'l

-with vthis latter modification being otherwise devic'eis herein shown and described which is of simple construction yet operable to periodically control the passage of high power. Moreover, the main electrodes by a comparatively low triggering voltage and the device operates with low dissipation over a desired kilovolt range for a Icommercially useful life of several hundred hours.

' Although several embodiments of the present invention have been shown and described, it is to be understood that still further modifications thereof may be made Without departing from the spirit and scope of the appended claims.

We claim: 1. A high pressure, triggered, spark-gap device disposed reentrant stems, a pair of main electrodes disposed in said envelope and forming an hermetic sealed end-closure for said reentrant steams for supporting a high current arc discharge upon the application of several kilovolts therebetween, an ionizable medium in said envelope at a pressure ranging from one to ve atmospheres, and a trigger electrode disposed closer to one of said main 'electrodes than to the other 'and The construction as shown operable upon the application of a potential between said trigger electrode and the adjacent main electrode to cause ionization of the ionizable medium and the initiation of the high current discharge between said main electrodes.

2. A high pressure, triggered, spark-gap device comprising an envelope provided with oppositely disposed reentrant stems, a pair of main electrodes disposed in said envelope and forming an hermetic sealed end-closure for said reentrant. stems for supporting a high current arc discharge upon the application of several kilovolts therebetween, an ionizable medium in said envelope at a pressure ranging from one to five atmospheres, and a disc-shaped trigger electrode of relatively large area disposed closer to one of said main 5, electrodes than to the other in the path of the T discharge between said main electrodeaand oper- .f

able upon the application of a potential between said trigger electrode and the adjacent main dium and the initiation of the high current discharge between said main electrodes.

3. A high pressure, triggered, spark-gap device comprising an envelope provided with oppositely disposed reentrant stems, a pair of main metallic cup-shaped electrodes disposed in said envelope and forming a glass-to-metal seal with said reentrant stems for supporting a high current arc discharge upon the application of several kilovolts therebetween, an ionizable medium in said envelope at a pressure ranging from one to ve atmospheres, and a trigger electrode coaxially disposed relative to the longitudinal axis of said main electrodes with its end passing through an opening in one of said electrodes in closely spaced proximity thereto and operable upon the application of a potential between said trigger electrode and the adjacent main electrode to causev ionization of the ionizable medium and the initiation of the high current discharge between said` main electrodes.

4. A high pressure, triggered, spark-gap device comprising an envelope, a pair of main metallic cup-shaped electrodes disposed in said envelope and forming a glass-to-metal seal with said fen'- velope for supporting a high current arc discharge l.im electrode to cause ion1zat1on of the ionizable me f 6 upon the application of several kilovolts therebetween, an ionizable medium in said envelope at a pressure ranging from one to five atmospheres, a trigger electrode coaxially disposed relative to the longitudinal axis of said main electrodes with its end passing through an opening in one of said electrodes in closely spaced proximity thereto and operable upon the application of a potential l'between said trigger electrode and the adjacent main electrode to cause ionization of the ionizable medium and the initiation of the high current discharge ybetween said main electrodes, and an insulating sleeve surrounding said trigger electrode except for the end adjacent the juxtapositioned main electrode to decrease the triggering potential necessary to otherwise initiate the high current discharge between said main electrodes.

EDWARD G. F. ARNOTT. CHARLES M. SLACK. CLARENCE E. DAWLEY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,004,012 Gerdien Sept. 28, 1911 1,513,561 Schroter Oct. 28, 1924 1,687,898 Schickerling Oct. 16, 1928 1,769,024 Hendry July l, 1930 1,816,619 Smith July 28, 1931 1,874,407 Young Aug. 30, 1932 1,878,341 Spencer Sept. 20, 1932 1,897,471 Foulke Feb. 14, 1933 1,986,397 Hund Jan. 1, 1935 1,999,649 Brett Apr. 30, 1935 2,034,756 Hansell Mar. 24, 1936 2,079,362 Rentschler May 4, 1937 2,098,301 Mendenhall Nov. 9, 1937 2,241,968 Suits May 13, 1941 2,263,032 Farnsworth Nov. 18, 1941 2,276,861 Penney Mar. 17, 1942 2,293,468 Knipp Aug. 18, 1942 2,400,456 Haine et al May 14, 1946 

